1. Field of the Invention
This invention relates to a detection circuitry and, more particularly, to an improved detection circuitry of the type designed to detect the start and the end of an incoming composite signal of the type such as frequency shift keying 50% amplitude modulated signal or pulse code modulated return to zero frequency shift keyed signal.
2. Prior Art
In many applications, it is important to provide a detection circuitry which is capable of detecting an incoming signal reliably and extremely fast, as in the space communications systems. There is a need for a receiver in the satellite or missile equipped to receive a short burst of command signal for self-destruct or other purposes. For example, should the missile go astray and pose danger, there is an urgent need either to correct the path or self destruct the missile.
In many areas of applications for communication purposes composite signal of a type such as composite frequency shift keying 50% amplitude modulated signal or pulse code modulated return to zero frequency shift keying signal is utilized as a command signal. Typically such a composite signal is repeated to introduce redundancy to assure that the receiver is given the opportunity to detect the signal. Yet the redundancy takes up time that could be utilized for communication of other signals.
Various attempts have been made to minimize the redundancy to save time but none heretofore have been completely satisfactory.